Silk screen printing press



Sept. 16, 1952 c. A. WING 2,610,579

7 SILK SCREEN PRINTING PRESS Filed Dec. 9, 1949 8 sheetssheet 1 INVENTOR. cums: H. mm.

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I Sept. 16, 1952 c. A. WING 2,610,579

SILK SCREEN PRINTING PRESS Filed Dec.- 9', 194 s Sheets-Sheet 2 ggmsfrozz. CHARLES A. WING.

fhm/Z h c. A. WING SILK SCREEN PRINTING PRESS Sept. 16, 1952 Filed Dec. 9, 1949 8 Sheets-Sheet 3 IN VEN TOR.

CHARLES A- WING- ATTORNEY.

Sept. 16, 1952 c. A. WING SILK SCREEN PRINTING PRESS 8 Sheets-Sheet 4 Filed Dec. 9, 1949 INVENTOR.

CHARLES A WING A-r'roR NEY.

Sept. 16, 1952 c. A. WING SILK SCREEN PRINTING PRESS 8 Sheets-Sheet 5 Filed Dec. 9, 1949 lllrll Iii I A INVENTOR. CHARLES A- w MG ATTORNEY- P 1952 c. A. WING 2,610,579

SILK SCREEN PRINTING PRESS Filed Dec. 9, 1949 8 Sheets-Sheet 6 v N 0 2 2. I a 27% Q '3 E5 :i I

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ATTORNEY.

Sept. 16, 1952 c. A. WING 2,610,579

SILK SCREEN PRINTING PRESS 8 Sheets-Sheet '7 Filed Dec. 9, 1949 -se /76 l -30 LP I12 was f i 5 13% I r14 0 INVENTOR.

C'f/ARLES A. (Ll/N6.

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ATTORNEY- P 1952 c. A. WING 2,610,579

SILK SCREEN PRINTING PRESS Filed Dec. 9, 1949 8 Sheets-$heet 8 I1 5/. l4 n i l8Z I ,na

l I -92 ,0 4s 96 5 H46 INVENTOR.

CHARLES A WING ATTORNEY.

Patented Sept. 16,1952

7 UNITED STATES -ATENT- OFFICE:-

" a V V .7 2,610,579 a f sILK SCREEN PRINTING PRESS Charles A. Wing, Ann Arbor, Mich.

Application December 9, 1949, Serial No. 132,129

' 18 Claims. 1

This invention relates to silk screen printing presses, and more particularly to an automatic silk screen printing press which is pneumatically operable and is adapted for the screening of any flat material such'as paper. show cards, cardboard, wood, metal or cloth.

The present invention provides a base upon which is mounted a suitable silk screen support, there being arranged upon the silk screen mounted on such support, and upon its under surface a suitable stencil. There is also provided a suitable stationary vacuum pad or work piece support on to which a card or other work piece is transported by the work slide. The workpiece hasa screening position as well as a discharge position, and furthermore has a pre-load position upon the base of the machine. The work slide is adapted by suitable grippers to engage-the work piece so that movement of the work slide in one direction will transfer the work piece to the vacuum pad-01f work piece support, after which the grippers will automatically release the work piece. A suitable squeege is carried by the work slide and is adapted upon the return movement of the work slide to bear upon the top surface of the screen and transfer therethrough printing material upon the work piece through a stencil upon said screen. Upon the next-transferring movement of the work slide the aforesaid pair of grippers engages the next work piece in its pre-load position and at the'same time a second set of grippers engage the work piece or card upon the vacuum pad so that as the new work piece or card is transferred to the work piece support, the first work piece is transferred to discharge position.

It is the object of the present invention to provide a continuously operable printing device wherein the work slide is intermittently reciprocating with respect to the machine base for transferring work sheets to printing position, simultaneously ejecting the previously printed work piece, and upon the return stroke of the work slide screening the work piece'to obtain a print thereon corresponding to the stencil upon the screen.

It is the further object of this invention to provide a simple compact mechanism which will operate with the maximum efiiciency for screen ing worksheets continuously.

These and other objects will be seen from the following specification and claims in conjunction with the appended drawings in which:

...Fig.' 1 is a right side elevational view of the machine.

Fig. 2 is an end elevational view thereof broken away and sectioned on line 2-2 of Fig. 1.

Fig. 3 is a, fragmentary partially broken away elevational section illustrating the construction of the pneumatic cylinder which operates the work slide of the machine. a

Fig. 4 is a partially broken away elevational section illustrating one of the work piece grippers andone ofthe screen frame adjustable locators.

Fig.- 5 is an. elevational view of a squeege sharpener construction.

Fig. fiis-an -enlarged section on line 66 0 Fig. 5.

Fig. 7 is a fragmentary plan view of the left end of the machine shown in Fig. 1 illustrating the locators for the work piece in pre loading position.

Fig. 8 is a fragmentary side elevational view illustrating the construction of the operating mechanism for the adjustable locators.

Fig. 9. is a, diagrammatic view illustrating the work slide cylinder, the vacuum operating cylinder, the four-way controlling valves and the various pilot valves together with their pneumatic connections.

Fig. 10 isa plan view of the screen support and screen assembly, partially broken away and sectioned to illustrate one of the adjustable locators upon said screen assembly.

Fig. 11 is a partially broken away plan view of the-machine.

Fig; 12 is a fragmentary elevational view of that portion of the machine shown in Fig 11, being the opposite side of the machine shown in Fig. 1.

Fig. 13 is a fragmentary plan view of the machine illustrating the work slide at the end of the work piece transferring stroke, also illustrating the construction of the retractable locator actuating bar. h

Fig. 14 is a fragmentary elevational view thereof which also illustrates the cam arm associated with the squeege holder and the spring loaded detent upon the work slide which holds the squeege in cammed up position on and during the work piece transfer stroke. 1 I Fig. 15 is a section taken on linefl'5-l5. of Fig. 11 and illustrating the positioning of the squeege at the end of the return screening stroke as it engages screening material before it is cammed upwardly for the next successive work piece transferring stroke.

Fig. 16 is an'elevational section illustrating the gonsgruction of four-way. valve I01 shown in g.

Fig. 17 is a diagrammatic section illustrating the construction of the control valve H3.

Referring to the drawings, the silk screen printing press includes a base H with hollow interior l2 to contain the various valve mechanisms and other pneumatic mechanisms hereafter described, there being provided upon one side a removable valve chamber cover l3 as shown in Fig. 1.

The base ll includes the horizontal platform [4 and the inclined instrument panel [5 with operating lever l6 thereon hereafter further described. Spaced upright piston rod supports I! and I8 extend upwardly from the base H upon one side of the machine to cooperatively receive and secure the respective opposite ends ofhollow stationary piston rod I9. I

Pneumatic cylinder 23 with spaced cylinder heads 2| and 22 at its opposite ends is reciprocally mounted upon piston rod l9 and transversely arranged work slide 23 is secured to cylinder 20 betweenthe cylinder heads 2! and 22 as shown in Fig l. Thus'the cylinder 2:: supports the work slide 23 upon one longitudinal edge for reciprocal movements relative to the bed l4 of the machine. The roller or rollers24 depend from the opposite side of work slide 23 and cooperatively bear upon the guide supporting strip 25 arrangedlong'itudinally on the machine bed 14. Thus thework slide operatin upon the stationafy piston rod [9 is guided and supported upon one Vsideso that reciprocal movements thereof are guided by a single member, and it is possible to swing the entirework slide upwardly around the piston rod to facilitate inspection of the u'ndersideof the work slide or that portion of the machine bed normally underneath the work slide.

Transverse journals 26, 21 and 28 are formed within work slide 23, and with suitable bushings 29 therein there is provided a transverse support for the trunnion bar 30 permittingrotary movements thereof. Transverse cam arm 3| depends from the outer end of trunnion bar 30 and is secured thereto at 32, said bar having centrally mounted thereon within the workslide 23 the squeege holder 33 shown in Figs. 1 and 2.

Hollow rectangular vacuum bed 34 is centrally mounted upon machine bed l4 and includes hollow vacuum chamber 35. the top surface 37 of the vacuum bed having formed therein aplurality of small openings 36. With the work sheet properly positioned upon Vacuum bed surface 31 vacuum may be applied to the under surface thereof through the upri ht passage 38 of the vacuum bed which terminates in the vacuum chamber 35. Suitable vacuum producing mechanism forms a part of the printing machine hereafter to be described, and it is contemplated that a suitable pipe will establish vacuum communication to the passage 38, as illustrated in Fig. 9 of the drawings hereafter described.

Hollow screen support 39 including horizontal flanges 39' as shown in Figs. 2 and is effectively' secured and positioned above the machine bed I4 providing a mounting for the rectangular screen support 40, across the lower surfacev of which extends a silk screen 4| to which is secured a stencil of the desired configuration.

Four work sheet gripper units 42 are arranged in pairs depending from the leading and rear edges ofwork slide support 23 as shown in Figs. 1 and 2, each of said grippers including a pivotal lower work sheet engaging arm 11, hereafterdescribed in detail in conjunction Withthe detailed description of Fig. 4.

A pair of spaced adjustable sequencecams 44 and 44' depend from work slide 23 for controlling certain pilot valves hereafter described with respect to Fig. 9 for achieving the cycle of opera'tions to be described, said sequence cams being laterally spaced as in Fig. 2, and longitudinally spaced as shown in Fig. 1.

There is also shown in Fig. 2 an interference cam 45 hereafter to be described but which under certain conditions is cooperatively engageable with the cam arm 3| for camming up the squeege carried by the squeege holder 33 to elevate the same with respect to the top surface 31 of the Workpiece supporting vacuum bed, as where no work piece has been positioned thereon.

Referring to Fig. 3 there is shown in enlarged partially sectioned detail one end of the pneumatic cylinder 20 including the spaced cylinder heads 21 and 22 which is reciprocally movable upon the hollow piston rod l9 whose respective opposite ends extend into the piston rod supports I! and I8, the latter of which is shownlin Fig. 3. Spaoedair line pipes 24- and 25' shown in Fig. 1 project upwardly from the interior l2 of the machine whil their upper ends join the ends of hollow piston [9, air line 24' being also shown in Fig. 3. V 7

The cylinder heads H and 22 are machined at 46 to receive therebetween the work slide 23 which is secured thereto for movement in unison with the reciprocal movements of cylinder 20 whichinterconnects said cylinder heads.

The disc4l .is suitably secured around-the end portions of piston rods 19 and is secured to the respective piston rod supports I1 and 18 as by the bolts 48. The piston rod 'includesa central portion of slightly increased diameter 49 from the opposite ends of which project the hollow tubular elements 50 whose exterior diameter is slightly less than the interior diameter ofthe pistonrod I9. As shown in Fig. 3 the tubular elements 50 project into the inner ends of piston rod elements is and are secured thereto as by the hollow transverse rivets 52.

Air line pipe 25 at its inner end at point 5| is threadably joined to tubular element 50 which forms a part of piston rod I9 so that compressed air through the interior 5| of tube 50 communicates with the interiorof rivet 52 through the opening 53, the opposite .ends of Which are in communication withannular air chamber 54 arranged upon one side of the piston to be described. Said air chamber is bounded upon one end by the annular pressure seal 55 which is retained by the gland56 and theguide bushing 51. Wiping ring 58 is also retained Within an annular recess in gland 56 for surfaceengagement with piston rod [9, whereas said gland 5B- is secured to cylinder head 22 asby the-bolts 59.

Cylinder 23 is a double acting cylinder movable upon the fixed piston rod IS. The compressed air for the cylinder is piped vin from each end to points on either side of the piston, one of whichv is shown inde'tail in 3 corresponding to cylinder head 22.

The piston for said cylinder includes spaced hardened rings 60 whichare-separated by a shoulder upon'the piston rod mid section 49,'said rings serving asa support for the cup washers 6| "having the ring 32 interposed therebetween.

The piston assembly is secured together'by a plurality of bolts 33 one of which is shown in Fig. 3. I V

The hardened ring plates *B4'are set into the cylinder head counterbore and are adapted tov contact the piston assembly for limiting the cylinder stroke. The inside diameterof-these; ring plates, one of which is shown injEigi 3,, closely fit; the enlarged" diameter of piston rod, midsection '49 to develop the cushioned". effect at each end'offithe cylinder stroke.

Cylinder head 22 is provided. with anexternal port 65 which communicates withthe interior of stationary pistonirod' l9 and the outer end ofiithe port or passage 65 is adapted for connection to one. end of the hydraulic cylinders. or pneumatic. cylinders of each of the. four gripper units hereafter described in detail.

Passage. 66 in cylinder head 22;.i's .j'olnediat'one. end to the pressure chamber 54: and is adapted for communication with thehorizontal passage 61 which delivers pressureflui'd, in this :casercompressed air 'to'thespace between piston 60' and theiring plate 64 showninFig. 3. However ball. relief valve. 68 is-positioned at: the: end of. passage 65 and retained by the spring 6-9 so that com-' pressed air in chamber '54 will first be delivered out through the: port-t5 for actuating all of i the gripper'units before movement-of the cylinder is effected. Thus this ball relief valv acts as a restrictionuntil the four gripper unitsiareclosed, after which 'the air 'pressurecontinuesto build up until air escapes past ball relief valve 68 and mid-section 49 of 'thepist'on rod. air isallowed to-pass through to the: piston face between ring plate. 6'4 and the normal piston rod diameter. This construction allows the closing of the work sheet gripper units prior tothe. start of the work slide cylinder stroke and further provides an accelerated start for the work slide cylinder 20.

Ball 'relief'valvefia can be adjusted by regulating the compression of spring 69, and this is effected by adjusting the threaded stem 10' which bears against said spring.

Transverse opening is formed within the ring plate 64 inconjunction with a" pressure sealed cone point '14 of the screw to thereby provide an adjustment of a the cushion-effect be-- tween the piston '60 and ring plate '64 'above'described; Air-return throughpassage -H on the opposite stroke of cylinder is blocked bythe 5 spring loaded ball valve 13 which seats into a countersink in ring plate '64.

The identical construction. less theexternal port 65 to the gripper units is also provided in the left cylinder head 2|, and this detail is not repeated or further described.

Referring to Fig. 4 one of the pneumatically operated 'four work sheet gripper units dz is shown in detail, each of said units being suitably secured upon the underside of the work slide 23 being arranged at its opposite ends'and upon its opposite sides as shown in Figs. 1 and 2, said gripper units being adapted to engage the work sheet at its leading edge for moving the same from the pre-load position 15 Fig. 1 to the screening position 1 6". The other set of gripper units which are mounted upon opposite sides of" the leading portion of the work slide. are adapted to also engage the leading edge of the work sheet as it rests upon the vacuum bedfor moving or. ejecting the work sheet from the screening posi-' tion to-the discharge position 16 indicated in Fig 1.

Now referring to Fig.4 the gripper unit 42 in cludes the upper: fixed; jaw. which; is. adapted 6, to. traverse horizontally during work, slide travel between the underside of the; screen'4 land the: top of the work sheet 16. Lower grip; H- with interchangeable gripping pad [8 is adapted to bearagainst the undersideof the worksheetat oneend andis-pivotally mounted at to a portion of the workslide 23.

Pneumatic cylinder 8| dependsfrom work slide 23 and intothe gripper housing-4 2i said cylinder having a nipple 82 at its upper end torwhich is connected'the pipe 8-3'joined-tothe exterior port: 65- from cylinder head-22 to thereby con'ductcompressed air to theyinterior ofrcylinder 8i. Reciprocal piston 84" ispositioned-within cylinvder 81: and. projects-therefrom and through a corresponding opening in the. gripper housing '2, with the outer end of said piston engaging lower gripper" arm 1.1 at.p.oint.85.- Upright; pin 86 is adjustably secured at'one. end'BB to" the. opposite'end' of gripper. arm 11 andcarries 'a. piston=8l:a-tits upper endwhichrisreciprocal within a corresponding opening 81" within gripper housing '62. A coil spring 89 is interposed between piston '81 and the housing 42 'so' that. upon: fluidi pressure release of piston; the spring :89 under. initial compression will .return theipiston 81 up wardlythus causing a-ydownward opening move-r ment of the lower'jawl l offtheiwork sheet-gripe per-mechanism. Itiisxcontemplated: thatti'n the operation of the machine that all fourrof the gri'pperunitsare energized. simultaneously from the" exterior pres-- sure port 65 from the cylinder-head 22. thermore all of the gripper "units willibe: released simultaneously when the'source. of compressed air to pipe 65, is: out off in the. manner=hereafter to be described.

Inxoperation the pair of gripper units at the rear edge of the 'work-slideengage the work sheet .in its'rpre-load position so thatsubsequent" movement of the cylinder 20' to the right" carries the work sheet to the vacuum bed 34. Thisis the transferring stroke-of the'work slide. At the end of this stroke the grippers are releasedso that on the return movement of the works'lide' the work sheet remains upon the vacuum bed as the squeege EM hereafter described bears down upon the silk screen 4| transferring screening" material through the screen. and the; stencili thereunder printing upon the work sheet which is retained upon the'vacuumbed as the squeege is traversed from right to leftover the. surface thereof.

At the end of the screening stroke cfthe Work slide the squeege is cammed' upwardly in. a manner hereafter described; and the gripperunitsat the rear end of the work slide again close upon the next work sheet in its pre-load position 16. As the work slide moves tothe right now on its. transferring stroke it is apparent that the newsheet will be carried over to rest uponthe "vac uum bed. Priorto this movement however, at the same time as said rear grippers engage the leading edge-of the second worksheet, the pair of grippers at the forward end of the workslide simultaneously engage the-leading edge of the first work sheet. Consequently the first sheet is withdrawn from the vacuum bed at the same. time as the next sheet is delivered thereto. In other words the rear grippers engage thesheet to move the same i. e. transfer the same to the: vacuum padrwhereas the forwardset of grippers areemployed toengage. the ipreviouslyprinted. work sheet-teremove the same from-the vacuums;

7 had to the discharge area IH shown in Fig. 12 hereafter to be described.

Now referring to Fig. '7 of the drawings the loading. platform for the machine is generally designated by the numeral 90. and the work sheet 16 has been positioned, thereon with its leading edge in the pre-load position designated by the arrow 16' of Fig. 1.

Locator 9| is arranged upon the machine bed It adjacent the loading platform 90 so as to receive thereunder the leading edge of the work sheet 'lfi, the end portion of said sheet bearing against the upright portion 9! of said locator. A pair of vertically adjustable locator pins 92 with rack gears 93 thereon are arranged for vertical reciprocal movement and are adapted to assume the elevated position shown in Fig. 8 to thereby engage the leading longitudinal edge of the work sheet 16.

Rotatable shaft 95 carries a pair of spaced pinions 94 which are in mesh with the rack gears 93 upon the two locator pins 92, said pins and said pinions being positioned within suitable housings 94' in the bed M. Lever arm 99 is secured upon the outer end of shaft 95 and is arranged transversely thereof so that a rocking movement of arm 95 in one direction or the other will. effect reciprocal movement of the locator pins 92. Transverse opening 91' at the upper end of arm 96 is adapted for attachment to longitudinally reciprocal or retractable locator operating bar H6 which is illustrated in Figs. 13 and 14 of the drawings.

Connector IT! is pivotally joined at [T8 to the upper end of the arm 99, the opposite end of the bar I16 extending loosely through an opening in the stop H9 which depends from work slide 23. Adjustable stop [80 is secured to one end of the bar I16, and a coil spring l8l is mounted upon bar H9 and interposed between stops I19 and I80. A second adjustable stop 182 is secured upon the bar I19 in spaced relation to the stop I89 so that when the work slide 23 traverses to the right from the position shown in Fig. 14 eventually the movable stop I19 will bear against stop I82 translating the rod [16 to the right suiiiciently to cause a retraction of the locators 92 shown in Fig. '7. By this arrangement the nextsheet to be transferred to printing position, having been previously properly located by 10- cators 9| and 92, is now free to be drawn from the pre-load position shown in Fig. 7 with locators 92 dropped down and out of the way.

From the illustration in Figs. 13 and 14 it is apparent that as the work slide reaches the position shown in Fig. 14 in completing the work sheet transferring stroke, the movable stop I19 will exert a thrust upon the rod H6 to the left through the agency of the coil spring IN. This has the effect of rocking the arm 96 which regulates the locators 92 so that the same will be elevated to the position shown in Fig. 8. Thus the locators 92 in cooperation with locator 9! are ready to effect the proper positioning of the next work sheet upon the loading platform 98 to assure that the same will be properly engaged by the grippers 12 at the rear end of the work slide 23 for the next work sheet transferring stroke. By this construction it is apparent that the locators 92 will be elevated to locating position just after the. preceding work sheet has been transferred thereover into printing position upon the vacuum bed. As shown in Fig. 7 a work sheet hold down clip 98 is also arranged upon machine bed l4 upon the opposite side of the loading platform 90 for cooperation with the corresponding hold down element 9| which forms a part of the locator 9l-9I'.

Referring to Figs. l0, l1 and 12 there are shown a pair of spaced horizontally extending printing screen supporting angle plates which include the horizontal portions 39' and the upright portions I41. The respective opposite ends of said angle plates have legs I48 which are secured upon the bed 14 and arranged in the manner shown in Figs. 11 and 12. The printing frame support also includes the transverse upright screen support 39 whose respective opposite ends lie between angle members I41 and whose lower edge bears upon and is suitably secured to hori-- zontal flange elements 39'.

Thus the silk screen frame is adapted to rest upon the angle iron elements 39' along its longitudinal edges, whereas the leading edge of the screen frame is arranged adjacent the cross piece 39.

Referring to Fig. 10 there are three locator buttons 99 two of which are mounted upon'angle iron [47 and one of which is centrally arranged upon the transverse bar 39. There are similarly mounted upon the screen frame 40 three adjustable locators which are adapted to cooperatively engage the three locator buttons as shown, one

of said locators being shown in section in Fig. 10, and also illustrated on an enlarged scale in Fig. 4.

Transverse bushings 190 are positioned through the screen frame 49 and secured in position by the nuts 19!. Locator pins it: are threaded through said bushings, a suitable. lock nut I04 being provided for securing locator pin I02 in a predetermined adjusted position. Said pin has a head J03 thereon by which the same may be rotatably adjusted. Once the locators have been properly'adjusted it is apparent that there will then be a predetermined positioning of th screen frame 40 upon its support 39. Thus should the screen frame be temporarily removed, as where a second screen is employed in the machine, then there is the assurance that when the first screen is replaced it will occupy the same relative position it originally had with respect to its support as well as with respect to the vacuum bed upon which a work sheet is positioned.

Very often there will be a plurality of screen sets as where multiple colors are desired to be printed upon the work sheet, and in that case it is desirable that the locators of each or" the screen frames be so adjusted that there will be proper registry between the respective screens when they are placed upon the screen support 39. Generally there is employed a separate unit for the pro-registration of screen sets which does not purport to be a part of the present invention. However a suitable illuminated stand is provided similar to the commonly known tracing table. There is provided work sheet locating points as Well as screen locating points which are identical with the locator buttons 99 shown in Fig. 10. In use a translucent work sheet is located upon the glass of the pre-registration unit and the first pass screen adjusted to laterally position and properly locate the impression relative to the work sheet. The adjustment is obtained by means of the three adjustable locators [G2 on the screen frame 48 shown-in Fig. 10. The first impression is transferred to the work sheet with suitable screening material by means of a manually operated squeege. The remaining screens in the set are then interchanged in the 'preeregistration unit. By adjusting the three 10- cators on each screen, each screen can be accurately registered with the initial screen and with one another. These pre-registered sets of screens canthen be loaded directly upon the screen support 39 with respect to the locating buttons 99 without furtherregistration for the different screening passes.

,As shown in Fig. 10 a wedge lock I35 is inter- ;posed between the screen frame 40 and the flange .I4;'I,.and said lock is expanded by means of the screw element I06 to thereby effectivelyseoure the screen frame 40 upon its supports 38' in proper pre-registered position.

There is shown in Fig. 9 a diagrammatic illustration of the work slide cylinder 23 illustrating the adjustable sequence cams 44 and 44 mounted thereon. Normally and as shown in Fig. 2 said cams depend from the lower side of work slide 23 however they are shown for purposes of illustration as mounted upon the cylinder 20 as it will be remembered that the work slide is secured to the cylinder 20 for movement in unison.

A vacuum operating cylinder I I9 is shown con- .nected to a vacuum cylinder I25 and there is provided four-way valve I01 for controlling the flow of compressed air to one end or the other oi. cylinder 20, and a second four-way valve I08 adapted for regulating the flow of compressed air to .one end or the other of a vacuum operating cylinder I I9. There are also shown a plurality of pilot valves 132, I35, I31 and I40 which are interconnected with the respective four-way valves I01 and I08 in the manner :now to be described.

Fig. 16 illustrates .the detail of construction of the four-way valve I01, and its construction is identical with four-way valve I08, both of said valves including a coil spring I09 which normally urges the movable valve element within the fourway valve to one extreme position. The valve element is moved in the opposite direction by compressed air, though hydraulic fluid could be employed in the present mechanism.

Compressed air pipe H may be joined to an exterior source of compressed-air or-on the other hand the compressed air source may be mounted within the machine base andconnect'ed to said pipe. Shut off valve III is arranged upon pipe 0 and there is also provided a start and stop operating lever I3 which is mounted upon the instrument panel'as shown in Fig. 11 and which is joined to and controls the two way valve H3 which is shown in detail in Fig. 17. 1 In one position of control lever IB'the valve element'within the valve II 3 is moved to the right permitting the flow of compressed air from pipe I l-0 out through delivery pipe H4. In another position of lever I6 the valve element is -so moved as to establish communication between .delivery pipe H4 and an exhaust port II 4' so that in effect the system will be bled whenever the supply of compressed air iscut off through operation of the lever I6.

Pipe 'I I4 is joined at its outer end to thecentral port of the four-way valve I0; as illustrated in Fig. 16. Similarly there is a branch pipe H5 which delivers compressed air to a corresponding central port of the four-Way valtie I88. A third branch pipe I I6 interconnects pipe 1 M with the normally-closed pilot valve 'idii the pipe -I I6 continuing from said pilot valve for connection to one end of the four-way valve I08.

' Thereis another branchpipe I 29 in which there is interposed manually controlled two-way valve -I3I whichvalveis opened-by-operation of the-foot pedal laoshown in Figs. 1 and 2. For auto- "10 matic operation of foot pedal I30 may be secured in depressed position by means of the latch I30. The pipe I29 is joined to pilot valve I32, and a second extension pipe I33 interconnects pilot valve I32 with the opposite end of fourway valve I01 as illustrated in Fig. 16. There is also a branch pipe I34 which interconnects pipe I33 and the normally closed pilot valve I35, .the latter having extending therefrom a suitable exhaust pipe I36.

Exhaust pipes H0 and I22 extend from fourway valves I01 and I08 and are connected to the exhaust muflier Haas shown. In Fig. 9 pilot valve I3! is open due to engagement of the se-- quence cam 44 therewith so that compressed air in pipe H6 can escape through pipe I39, through the pilot valve I31 and out through the exhaust pipe I38. When the lever I6 is turned to open position compressed air is delivered to pipe I29 and if the pedal I30 isdepressed the fluid will ifiow through pilotvalve I32 which isopen and thence through pipe I33 to the end of four-way valve I 01 causing the valve element therein to move to the right of the position shown in Fig. l6. The coinpressed air will then flow through the four-way valve and out through the pipe 24"and into the cylinder 20 upon the right side of its stationary piston 60. V 7

As previously described in detail thecompressed air is first available through the exterior port 65 which connects each of the gripper units 42 for closing the same. After the pressure builds up the ball valve 6B Fig. 3 will open and the compressed air will flow into the cylinder causing movement to the right which corresponds to the workpiece transferring movement or the work slide of the machine. And the cylinder will continue untilit reaches the limit of its movement to the right. However before this occurs the sequence cam 44 will engage and open the pilot valve I40 and this will permit the flow-of coinpressed air to the four-way valve I00 for operating the same in exactly the same manner as fourway valve It! above described. It will be noted that sequence cam 44 has moved away from pilot valve I37 so that the exhaust pipe I39--I.3B is closed.

The four-way valve I08 is now set so that com pressed air delivered through the pipe I I5 will flow through pipe IIB to the left side of vacuum operatingcylinder IIS which contains piston I20 and piston rod I23 connected thereto. Exhaust from the opposite side of piston I20 returns to four-way valve I08 through the pipe I2I and exhausts therefrom through theexhaust pipe I 22. At the same time while cylinder 20 is moving to the right exhaust fluid from the opposite side of piston 60 is returning through pipe 25' to fourway valve I0! and exhausted therefrom through the pipe II8. It will be noted that flow; control adjustable valves II'I are arranged in the cylin .der lines 24 and 25 whereby the speed of movement of cylinder 20 can be regulated.

Piston rod I23 has upon its opposite end a vacuum inducing piston I24 which reciprocates within vacuum cylinder I25, and it will be seen that the movement to the right of piston I20 effects a corresponding movement of piston I24 creating a vacuum upon the left side of piston I24, and this vacuum is communicatedto the vacuum bed 34 by the pipe I26. In the cycle of operation it is apparent that after cylinder 20 completes its transferring stroke to the right during which a work sheet has been moved into position upon the vacuum bed 34, then thevacuum circuit through the pipe I26 is energized to effectively retain the work sheet in position upon said bed during the return printing stroke of the cylinder 25 to the left. It will be noted that as soon as pressure fluid is cut off from the right hand end of cylinder 26 it will also be cut off from the pipe 65 which leads to the gripper units 'so that these will all be released so that there will be no interference of the work sheet with the return to the left of the work slide.

A cam I28 is mounted upon piston rod I23 and in Fig. 9 is shown in engagement with pilot valve I32 opening the circuit therethrough so that pressure fluid was available in pipe I33 for operating four-way valve IU'I. piston I20 moves to the right in sequence to the right hand movement of cylinder 2t cam I28 will be disengaged from pilot valve I32 and the flow therethrough stopped. As soon as cam I26 engages pilot valve I35 opening the same it isapparent that pipe I33--I34 will exhaust the fluid from four-way valve I6? through the exhaust pipe I36, thus causing an automatic spring operated reversal of four-way valve I61.

As shown in Fig. 16 this reversal directs pressure fluid from pipe II4 to cylinder pipe 25 initiating the return screening movement to the left of cylinder ZIL'and now the exhaust from the other side of said cylinder returns to four- Way valve I61 through pipe 24.

Now as cylinder 26 returns to the position shown in Fig. 9 sequence cam 44 again opens the pilot valve 31 permitting fluid to exhaust therethrough, and this causes an automatic reversal of four-way valve I08 due to the action of its spring I69. Then the pressure fluid in pipe H is delivered to the right end of vacuum operating cylinder I26 through the pipe 12 I, and this causes movement of its piston I back towards the position shown in Fig. 9, releasing the vacuum in pipe I26 and consequently releasing the Work sheet 16 from the vacuum bed 31. Thus it appears that at the end of the leftward screening movement of the work slide and cylinder 20, the work sheet will be automatically released so that upon the return transfer movemeint of said work slide to the right the leading grippers will engage said work sheet and eject the same onto the discharge area I'll Fig. 12.

At the same time that vacuum is released in pipe I26 it is apparent a vacuum condition is created upon the right side of piston I24 and this vacuum will be transmitted through the pipe I2I, pipe I4I to the vacuum operated auto matic loading mechanism diagrammatically indicated at I42 and having the loading arm I43 which is so constructed as to pick up the top sheet from a stack of work sheets and transfer the same to the loading platform 93 of Fig. 7. There is also provided a branch pipe I44 connetced to an automatic vacuum operated work piece pick off mechanism I45 with operating arm I46 which is adapted to remove the printed sheet from its discharge position 76" indicated in Fig. 1. r

The structure of the vacuum operated automatic loading and pick off mechanism form no part of the present invention and therefore further description thereof is omitted. It will be noted however that both units I42 and I45 will be operated simultaneously. a a

The present printing machine operates upon a step cycle in that the vacuum operating cylinder I I9 actuates the control for the work slide cylinder 20, and the latter actuates the control for the However as soon as 12 vacuum operating cylinder H9. This arrangement insures exactly repetitive cycling and eliminates any necessity for further coordinating the relative movements of the two cylinders.

A further merit in this instance is that the step cycle arrangement allows the work slide cylinder to continue on to the fixed end of its stroke as necessary for the successful operation of the printing unit,'after tripping the pilot valve I48 which actuates the control valve I08 for vacuum operating cylinder He. It will be noted that vacuum cylinder I provides two difference circuits, only one of which is used for the vacuum bed 34. The remaining circuit can be applied to the vacuum requirements of the automatic loading and plckoiT mechanisms I42 and I45. Vacuum is developed in this extra circuit before the work sheet transfer stoke during which stroke the next work sheet would be moved to preload position or pickofi from the discharge area.

Referring to Figs. Hand 12 there is provided upon the bed I4 the stop I49 with adjustable pin I56 projecting therefrom, and including the lock nut I5I for setting said pin in adjusted position. As shown in Figs. 11 and 12 there is a second stop I52 spaced from stop I} including stop pin I53 and lock nut I5I. The stops I49 and I52 are arranged so as to be in the line of travel of the knock-off or cam arm 3I which extends from the trunnion shaft 30 upon which the squeege holder 33 is mounted. It is the purpose of the stops I55] and I53 to intermittently engage the lower end of the cam arm 3i, with cam arm 3I engaged by the stop I53 at the end of the travel of the Work slide 23 so that the squeege is cammed upwardly out of engagement with the screen 4| for the return transferring stroke of the carriage or work slide 23.

Fig. 12 indicates the angular cammed up position of the squeege holder 33 and its squeege I54, and there is shown particularly in Fig. 14 a notch I6! formed in the upper portion of knockoff arm 3I, which in the position shown in Fig. 12 is adapted to receive the detent I69 which extends through housing I68 and which includes a coil spring I10 normally urging said detent to the left. This thus assures that the squeege will be maintained in its cammed up position during the transferring stroke of the carriage.

Now at the end of the transferring stroke such as illustrated in Fig. 14 the stop I operatively engages the arm 3| and pivots the same to the position shown in Fig. 14, disengaging the detent I and at the same time causing the squeege I54 to be cammed down into transfer position ready for the return printing movement of the work slide 23 to the right.

As shown in Figs. 11 through 15 transverse rod IE3 is secured at I64 adjacent the outer end of trunnion rod 30 to which is secured the squeege holder 33. Weight I65 is slidably adjustable upon the rod I63 and may be secured in position by the set screw I66. By this construction a rotary thrust is delivered to shaft 30 to thereby regulate the downward pressure of the squeege I54 with res ect to the screen 4 I The vacuum bed 34 is provided to hold the work sheet in screening position however under some conditions no sheet may be delivered to the vacuum bed. 'In this case it would be undesirable to have the squeege bear down upon the screen and pass over the vacuum bed, as this would result in printing material being drawn thereinto. This avoided by an interference cam communication with vacuum chamber 35. Cylindrical hollow extension I60 is joined to the bed 34 for registry with said opening, and piston I62 is positioned within said opening. Piston rod 45 is joined to said piston and projects outwardly through extension I60 and by virtue of a coil spring :I6I is normally maintained in the positionshown'in Fig. 11 ice. in the path of squeege actuatinglever 3|. 'Whenvacuumis introduced into the bed 34 immediately prior to the start'of the screening stroke of the squeege, and if a work sheet is in position upon bed 34, then saidpiston and. rod will move inwardly under atmospheric pressure so as to be out 01' the path of the squeege arm 3 I.

Thus the squeege will be automatically cammed up upon the screening stroke when no sheet is upon thevacuum bed.

As shown in Fig. '11 the control panel I5 includes thereon speed control I12, operating pressure gage I13 and Ii-nepressure gage 114. Speed ta'ining'ly receive throughoutits width the squeege body I55 which retains throughout a longitudinal slot at its lower end the rectangularly shaped squeege blade I54. This bladeis secured within the lower end of squeege body I55 by the transverse screws I59, said squeege projecting below its holder or squeege 'body as shown in the drawings.

Near the squeege blade end the body I55 has formed upon its opposite sides a plurality of equally spaced longitudinally extending grooves I56;one of which upon each side of said body is adapted to receive a corresponding projecting rib I51 Fig. 12 extending: inwardly from opposite sides of the interior walls of the squeege holder 33. Elongated slots I58 are also formed in the squeege body I55 and are adapted to receive inwardly projecting studs from the mounting face of the squeege holder '33.

As the screening lower'edge of the'squeege I54 wears and is sharpened the squeege body I55 can be moved down relative to the mounting ribs I51 of the squeege holder. For wear between the spacings of the grooves I56 of the squeege body accommodation can be made in the allowable squeege contact angle upon the screen 4|. Furthermore the body I55 is reversible so that both edges of the squeege blade I54 can be "used before sharpening. To remove orreversesaid blade it is merely necessary to remove the screws I59. As shown 'in Fig. the squeege body I is retained within the squeege holder 33 as by the studs I55.

A-squeege sharpening device is shown'in Fig. 5 of the drawings which includes the base I and thesqueege supporting oppositely arranged guide elements I66 and which include the inturned ledges I81 upon which the squeege bodyv 'I 55 slidably rests duringsharpening .of the squeege 154. The squeege guides are supported in parallel spaced relation to the base I85 by the links I89 whichare pivotally joined to the base I85 at points I90 and pivotally joined to the guides I86 at points I191 Adjusting shaft I92 rockably anchored at I93 within base I85 is threaded at its opposite end at I94 .to .adjustably engage the link I89 at I95. By rotation of member I92 in one directionor the other'it'is possible to regulate the height of the guides I186 relative .to the base, at the same time regulating the relationship between the lower edge of squeege I54 and the abrasive sharpeningstrip I98.

Said strip is arranged upon the rolls I91 which are journaled at 2flI to "the upright members I96 upon the base I85. Ratchets I99 engage the ratchet .teeth 2'86 upon the rolls I91 for securing adjustably the abrasive 'striprelative to the squeege I154. Thus the :height of the squeege may be regulated and furthermore a double ratchet feed provided :for the abrasive material I98. Sharpening is accomplished by drawing the squeege body I55 back and forth through the guides I86 over the abrasive strip I98. The squeegeis guided .on the interior sides and shoulders of said guides adjacent .the' blade, whose surfaces are parallel with the guide grooves I56 formed in the squeegebody I55. Here also the interior walls of the guides I86 have formed thereon. a longitudinal rib I88 :Fig. '6 which is adapted to cooperatively nest within .a' corresponding groove I56 in the squeege body.

Now referring to Fig. .15 the work slide 23 :is shownapproximately at the end of the screening stroke just prior to thecamming up of the squeege holder 33 by the St0p..I.53 shown in. Fig. 12. Screening material by which the printis formed is piled up at I83 upon the silk screen 4I adjacent the screen frame 46, and the squeege blade I54 dips into said material before being eamm'ed upwardly. Thus the squeege carries suificientscreening material for printing upon the next printing stroke of the carriage 23.

Operation To operate the silk screen printing machine above described it is of course necessary that the shut-ofi'valve III Fig. am open. Also thecontrol arm I6 upon the instrument panel must bemoved to on position after which the operator depresses the footpedal I30, and this starts the machine cycle.

The grippers'42 close upon the work sheet 16 which was previously properly located inpre-load position 16 vFigul as bythe locators 9;! "and .92 of Fig. 7.

The work. slide 23 then. moves to the right transferring thework sheet to screening position upon the vacuum bed 34. At the end of this transferring stroke the squeege I54 is cammed down to screening position by the engagement of the cam arm 3I with respect to the stop I50, and this is illustrated in Fig. 14.

The vacuum bed is now provided with a vacuum source and the work sheet is secured thereon ready for the returnscreening stroke of the work slide and squeege. However before the return screening stroke the grippers 42 releasethe work sheet 16, and then the work slide and fthesqueege carried thereby return on the'screeningf stroke with the squeege I54 depressing the silk-screen '41 tocontact the Work sheet'l6.

Near the end of this screening stroke as shown in Fig. 15 the squeege momentarily dips into the screening material I83 at the left hand side of the screen picking up screening material forv the next cycle, after which it is cammed upwardly to clear the screen in the manner illustrated in Fig. 12, with the stop I53 operatively engaging the knockoff arm 3| connected with the squeege holder 33. This completes the first cycle.

As shown in Fig. 14 the work slide 23 as it nears the end of the screening stroke to the right operates the locators 92 of Fig. 7 depressing the same so that the next work sheet I6, which was preiously properly located before depression of said locators, can be properly gripped and transferred to the vacuum bed upon the next successive transferring stroke of the work slide. At the same time the forward set of grippers 42 upon the leading end of the carriage 23 or work slide engage the work sheet which has previously been printed and now transfer this work sheet to the discharge area III which is illustrated in Figs. 11 and 12 and which corresponds to position 56" of Fig. 1 and Fig. 13. Position I6 shown in Figs. 1 and 13 indicates the printing position of the work sheet .16 upon the vacuum bed 34.

The machine can be stopped at any point in the cycle by moving the operating lever IE to the oil? position, and in this case and as shown in Fig. 1'7 this will have the eifect of bleeding both of the four-way valves I01 and W8 Fig. 9.

For automatic continuous operation the foot pedal I 36 may be secured in depressed position by the latch I.

In Fig. 9 H2 indicates an oil vapor supply to the pneumatic system which is effective to lubricate the cycle valves and the cylinders shown.

Having described my invention, reference should now be had to the claims which follow for determining the scope thereof.

I claim:

1, In a silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, and a pair of work sheet gripping elements depending from said slide for transporting a work sheet from said bed to said work sheet support under said screen.

2. In a silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen. a squeege carried by and depending from said slide and movable upon the surface of said screen, and a pair of work sheet gripping elements depending from said slide for transporting a work sheet from said support onto said bed.

3, In a silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a pair of work sheet gripping elements depending from the rear edge of said slide for transporting a work sheet from said bed to said work sheet support, and a second pair of work sheet gripping elements depending from the leading edge of said slide for simultane ously transporting a work sheet from said support onto said bed.

4. In a silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support'in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a hollow piston rod and piston secured at its ends to said bed with fluid outlets formed in said rod adjacent opposite sides of said piston, a pneumatic cylinder reciprocally mounted upon said rod and joined to said slide, said cylinder including a pair of cylinder heads at its opposite ends, each of said heads being cooperable with an outlet opening defining a pressure chamber, there being a channel in said head interconnecting said chamber and one side of said piston, and an adjustable ball relief valve in said channel adapted to open upon the building up of a predetermined pressure in said chamber.

5. In a, silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above-and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending fromsaid slide and movable upon the surface of said screen, a hollow piston rod and piston secured at its ends to said bed with fluid outlets formed in'said rod adjacent opposite sides of said piston, a pneumatic cylinder reciprocally mounted upon said rod and joined to said slide, said cylinder including a pair of cylinder 7 heads at its opposite ends, each of said heads being cooperable with an outlet opening defining a pressure chamber, there being a channel in said head interconnecting said chamber and one side of said piston, and an adjustable check valve in said channel adapted to open permitting restricted exhausting of fluid from said cylinder to said pressure chamber to cushion the movement of the cylinder head relative to said piston.

6. In a silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a pair of work sheet gripping elements depending from said slide for transporting a work sheet from said bed to said work sheet support under said screen, each gripping element including a stationary grip projecting inwardly for movement above said support and under said screen, a movable grip pivoted to said stationary grip and extending inwardly for similar movement, fluid motor means for moving said latter grip into cooperative relationwith said first grip, and a coil spring interconnecting said grips to open said movable grip upon pressure release of said means.

7. In a silk screen printing press, a horizontal bed, a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a pair of work sheet gripping elements depending from the rear edge of said slide for transporting a Work sheet from said bed to said work sheet support, and a second pair of work sheet gripping elements depending from the leading edge of said slide for simultaneously transporting awo'rksheet from said support onto said bed, eachgripping element including a stationary grip -projecting inwardly for movement above'said support and under said screen, a movable grip pivotedto said stationary grip and extending --inwardly for similar movement, fluid motor means for moving said latter grip into cooperative relation withsaidfirst grip, and a coil spring interconnecting said grips to open said movable grip upon pressure release of said means.

8. Ina silkscreen printing press, a horizontal bed, a-work sheet support thereon, a screen .mounted upon saidbed and positioned above and adjacent said supportin parallel spaced relation,

said lattergrip into cooperative relation with said first grip, and a coil spring interconnecting said grips to open said movable grip upon pressure release of said means, a source of pressure fluid, and conduits'joining'said source and each of said fluid motor means for simultaneously opei'atingsaid gripping elements.

9. In a silk screen printing press, a horizontal bed, ,a work sheet support thereon, a screen mounted upon said bed and positioned above and adjacent said support in parallelspaced-relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a pair of worksheet gripping elements depending from the rear edge of said slide for transporting a work sheet from said bed'to said work sheet support, a second pair of work sheet gripping elements depending from the leading edge of said slide for simultaneously transporting a work sheet from said support onto said bed, each gripping element-including a stationary grip projecting inwardly for movement above said support and under said screen, a movable grip pivoted to said stationary grip andextending inwardly for similar movement, fluid motor means for" moving said latter grip intocooperative relation with said first grip, and a coil spring interconnecting said grips to open said movable grip upon pressure release of said means, a source- 0f pressure fluid, and conduits' joining said source and each of said fluid motor-means for simultaneously operating'said grippi elemerits.

10.;1'11 a silk screen printing press, a horizontal bed, a work sheet support thereon, a'screen mounted upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movably mounted upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a piston rod and piston secured at its ends to said bed, a pneumatic cylinder reciprocally mounted upon said rod and.

joined to said slide, a pair of work sheet gripping elements depending from said slide for trans porting a work sheet from said bed to said work '18 sheet support under said screen, each gripping element including a fiuid motor, a pressure chamber in said cylinder, and a conduit interconnecting saidpressure'chamber with each of said fluid motors.

. 11. In asilk screen printing'press, a horizontal bed, a work sheet support thereon, a screen mounted'upon said bed and positioned above and adjacent said support in parallel spaced relation, a reciprocal slide movablygmouned upon said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a piston rod and piston secured at its ends to said bed, a pneumatic cylinder reciprocally mounted upon said. rodand joinedto said slide, a pair of work sheet gripping elements depending from the rear edge ofsaid'sli'de for transporting a work sheet from said bed to said work sheet support,and a second 'pair of work sheet gripping ,elements depending from the leading, edge of said slide for simultaneously transporting a worksheet frornsaid support onto said bed, each gripping element in-= eluding a fluid motor, a pressure chamber in said cylinder, and a conduit interconnecting said pressure chamber with each of said fluid motors.

12. In a silk screen printing press, a horizontal bed, a work sheet support thereon, .a screen mountediupon said bed and positioned ,above and adjacent said supportinparallel spaced relation, a reciprocal slide .movably mounted .upon

said bed above said screen, a squeege carried by and depending from said slide and movable upon the surface of said screen, a pistonrod and piston secured at its ends to said bed, a'pneumatic cylinder reciprocally mounted upon said rod and joined to said slide, a pair of work sheet gripping elements depending from said'slide for transporting a work sheet from said bed to said work sheet support under said screen, each gripping element including a fluid motor, a pressure chamber in said cylinder, a conduit interconnecting said pressure chamber with each of said fluid motors, and a ballrelief valve in said cylinder in communication with said pressure chamber permitting energization of said motors before actuation of said cylinder;

13. In a silk screen printing press, a horizontal bed, a work sheet supporting vacuum bedineluding a vacuum chamber, and. a plurality of spacedoutlets in the top of said bed incommunication with said chamber, a Vacuum source, a conduit interconnecting said source and said vacuum chamber, a reciprocal slide movably mounted upon saidxhorizontal bed above said vacuum bed, a screen mounted upon said horizonrod intothe path of movement of said camming arm for engagement therewith, said piston be" ing retractable under atmospheric pressure upon the maintenance or" a vacuum within said vacuum chamber.

14. In a silk screen printing press, a horizontal bed, a reciprocal slide movably mounted upon said horizontal bed, a reciprocal fluid motor upon said bed joined to saidslidaasouroeof pressure fluid, .aiourway valve joined thereto,.:a .pair of. conduits interconnecting said .valve with opposite ends of said motor, .a workpiece-.supportingvacuum bed upon said horizontal bed, a vacuum cylinderhavinga reciprocal piston and rod therein,..a conduit. interconnecting oneend of said .vacuum cylinder with said-vacuumbedravacuum operating cylindenareciprocal piston there- ..in joined to thevacuum cylinder piston rod,--a .second fourway valve joined .tosaidsource of pressure .i'luid, and a .pairof conduits interconnecting said latter fourway valve with-Opposite .endsof said vacuum operating-cylinder.

.15. In a silk screen printing. press,.a horizon- .tal bed, a reciprocal slide movably mounted upon said horizontalbecLa reciprocal fluid motor upon said bed joined to said s11de,-a source of pressure fluid, a fourway .valve .joined .thereto, a pair of .conduits interconnectingsaid-valve with opposite ends of .saidmotor, a work pieoe-supportingvacuum bed upon said horizontal bed,.avacuum cylinder having a reciprocal piston androd therein, aconduitinterconnecting one end of "said vacuum cylinder-with said vacuum bed, avacuum operating-cylinder, a reciprocal piston therein joinedto the vacuum cylinder piston rod, a :secondfourwayvalve joined to saidsource of pressure. fluid, and apair of conduits interconnecting said latter fourway valve with opposite ends of said vacuum operating cylinder, S8,1d*V3,1V8Sfin eluding. spring. biased valve elements-therein normally directingpressure fluid 130171180116 endsof said motor and vacuum operating-cylindenand separate valve operating conduits respectively interconnecting said source and said valves; for reversing the operation thereof.

16. Ina silk screen printing press, a horizontal bed, a reciprocal slide movably-mounted uponsaid horizontal bed, a, reciprocal fluid motor upon said .bed joined tosaid slide, a source of pressurefluid,

a fourwayvalve joined thereto, ,apairof conduits interconnecting said valve with opposite ends of said motor, a workpiecesupporting-vacuum bed upon-said horizontal bed,-a vacuumcylinder having a reciprocal; piston and roditherein. a conduit interconnecting 'oneendof .said vacuum cylinder with said-vacuum bed,;a:vacuumq.operat ing cylinder, a reciprocalpistoniherein joined to the vacuum cylinder piston rodyaisecondfourway valve joined to. said :source :;of:.pressure .iiuid,

and a pair of conduits interconnecting said latter fourway valve with opposite; endsv of said vacuum operating cylinder, said :valves including spring biased .valve .elements :therein normally directing pressure .fluid to'the one endso'f said motor and'vacuum operating cylinder, separate valve operating conduits respectively interconnecting .saidsource and. said valves for reversing the operation thereQLseparate pilotivalves in said valve operatingconduits to'initiate'vvhen actuated the'fiow of pressure .fluid'therethrough to operate the.:respective 'fourway valve, and separate exhaust pilot valves in said valve operating conduits -.to exhaust when'actuated respectively 20 the pressure fluid from said valve operating conduits.

.17 Z In-a silkscreen printing press a horizontal .bed, a ,reciprocal slide -.movably mounted upon said horizontal bed,a reciprocal fluid motor upon saidcbedjoined to-saidtslide, asource of pressure ..fluid, .a-fourway valve joined theretoya pair of .conduits interconnectingsaid 'valve with opposite ends of-said motor,:a--Worl piece supporting vacuum-bed uponsaid horizontal bed, a vacuum cyl- 18. a;sill :scr.een printing press, a. horizontal ,bed,-a reciprocal slidermovablyimounted upon said -.horizontal;-bed,-:a;reciprocal fluid-.motor upon said bed joineditosaidslide, aisourceof'pressure fluid, a fourway'valve'joined thereto, a'pair of conduits .interconnecting'said valve with opposite ends of said motor,"-.aiworkmiece: supporting vacuum bed upon saidhorizontal bed, avacuum cylinder havingza reciprocal piston'andirod therein, a conduit interconnecting one:end'of said vacuum cylinder vrithsaidivacuumbed, aavacuum'operating cylinder, a reciprocal pistonitherein joined to the vac- .uumcylindervpistonrod, a second fourway valve joined to saidsourceof'pressure fluid, a pair of .conduits interconnecting .said latter fourway valvewithnpposite .ends of said vacuum operating .cylinder,.a vacuum operated Work sheet load- .ing and pick-off devices upon said horizontal bed, and a .conduit interconnecting the other end of said vacuumcylinder'and said devices to intermittently energize the same.

CHARLES A. VYING.

.. REFERENCES CITED :The,following'referencesiare ofrecord in the file of this patent:

" UNITED STATES PATENTS Number Name Date 1,095,126 Rogers et al.. Apr. 28, 1914 1,184,626 Cross May 23, 1916 1,732,074 -Weiler. Oct. 15, 1929 1,832,828 Borregard -Nov. '17, 1931 2,039,909 .Kem .etzal.v May 5, 1936 2,121,491 'Soubier June 21,.1938 2,207,818 Perry'et-al. July 16, 1940 2,229,346 Shurley Jan. 21, 1941 2,267,596 Montague Dec. 23, 1941 2,321,134 :Fleisheret a1 June 8, 1943 2,355,930 Thorne Aug. 15, 1944 2,383,947 Wenselet;al. Sept. 4, 1945 

